The invention relates to a functional unit for adjusting a brake pad of a disc brake such as a commercial vehicle disc brake.
The functional unit is arranged with its essential functional parts in the interior of a brake caliper. The brake force which is applied via a rotary brake lever is transmitted via the guide rail (bridge), against which the brake lever bears, to a brake pad which bears against the guide rail and can be pressed against a brake disc in the case of braking.
To this end, pressure pieces are assigned to the adjusting spindles on the sides which lie opposite the brake lever, for bearing against the brake pad.
In order to compensate for an air play which changes in a wear-induced manner between the brake pad and the brake disc, the adjusting spindles are moved in the direction of the brake disc, to which end a wear adjuster engages into one of the adjusting spindles, which are configured as a threaded tube. The wear adjuster rotates the adjusting spindle upon actuation of the brake lever.
In order to rotate both adjusting spindles homogeneously, a synchronizing device is provided which is arranged as a traction mechanism drive on both adjusting spindles such that it cannot rotate.
Here, the traction mechanism drive consists of two drive wheels, of which in each case one is held in a rotationally locked but axially displaceable manner on an associated adjusting spindle, whereas a traction mechanism, preferably a link chain, a toothed belt, a perforated belt or a string of beads, engages in a positively locking manner into an external toothing system of the drive wheels. The synchronization of the two adjusting spindles such that the connected brake pad runs with a continuously identical gap size with respect to the brake disc has taken place up to now after extensive assembly of the disc brake.
Problems arise, however, if components of the mechanism, which is positioned in the interior of the brake caliper, are damaged. In order to repair or replace them, the brake caliper has to be opened on its side which faces the brake disc, where it is sealed by way of a closure plate which is screwed to the brake caliper.
Here, passage openings of the closure plate for the adjusting spindles are closed in each case by a folding bellows which is held on one side on the adjusting spindle and on the other side on the closure plate. The folding bellows also have to be removed, just like the individual components of the functional unit of the generic type.
Since a replacement of the damaged parts is, in practice, impossible on account of the work-intensive dismantling and assembly, including the safety-relevant setting of the functional unit, in particular renewed synchronization of the adjusting spindles, the entire disc brake is usually replaced.
This naturally represents an extremely unsatisfactory state with regard to economics.
The invention is based on the object of developing a functional unit of the generic type in such a way that more economical operation of the disc brake is made possible, in particular by way of a reduction of repair costs.
This object is achieved by way of an apparatus for adjusting a brake pad of a disc brake, having the following functional parts: a guide rail, two adjusting spindles which are arranged parallel to and a spacing from one another in the guide rail and are held in an axially movable manner, and a synchronizing device for the synchronous adjustment of the adjusting spindles. The functional parts are preassembled to form a modular unit.
A whole series of advantages arise from the fact that, according to the invention, the functional unit, above all with the specific functional parts of the guide rail, the adjusting spindles which are arranged parallel to and at a spacing from one another and are held in a rotationally and axially movable manner in the guide rail, and the synchronizing device, are preassembled to form a modular unit.
The functional setting of the synchronizing device can thus be performed at the factory, which naturally simplifies the assembly of the functional unit substantially.
Here, the synchronizing device consists of the components which are defined in the introduction of the description, above all a traction mechanism drive which, according to a further concept of the invention, is arranged on the outlet side of the adjusting spindles from the guide rail. However, the arrangement of the traction mechanism drive on the opposite side of the guide rail, but inside the brake caliper, is also contemplated. In this traction mechanism drive, the drive wheels are configured in such a way that an axial adjustment of the adjusting spindles with respect to the traction mechanism drive is possible, and secondly the drive wheels are connected in a rotationally fixed manner on the adjusting spindles.
Secondly, the drive wheels are mounted in an axially secured manner in relation to the longitudinal axial direction of the adjusting spindle but such that they can be rotated on the guide rail.
In addition to simpler assembly the invention is also distinguished by the fact that other functional parts which are arranged in the brake caliper, for example other parts of the brake application device, can be removed and replaced without problem if required, namely in the case of a necessary replacement, since the preassembled module which is present as one functional unit in a structurally assembled manner can be removed from the brake caliper without problem, with the result that free access to the interior of the brake caliper is possible.
Subsequently, after replacement of the corresponding functional part, the module can be inserted again, either in a completely new state or merely the removed, functional module.
A further embodiment of the invention is to be considered particularly advantageous, in which the closure plate and the folding bellows are likewise taken into consideration as functional parts during the preassembly of the module.
The correct setting of the synchronizing device can be seen, for example, by the attachment of a tamper-proof marking, for example in the sense of a seal which, after setting at the factory, is preferably attached in the sealing region between two functional parts which can be moved relative to one another.
However, it is also contemplated to couple the preassembled closure plate and the guide rail to one another by a seal or a lead seal. In every case, it is ensured that a complete module in the original state is used.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.